1. Field of the Invention
The present invention relates to an image forming apparatus such as a fax machine, a printer, a copier, and a multifunction peripheral, and a control method of the image forming apparatus.
2. Description of the Related Art
There are conventional techniques for controlling a power-saving mode of an image forming apparatus such as a fax machine, a printer, a copier, and a multifunction peripheral. For example, an ASIC including a programmable sequencer configuring a programmable control circuit with which the power supply can be controlled, is used to perform control operations for switching/returning to a power-saving status and to monitor a network during a power-saving status, and to return to the regular operation mode from a power-saving status via a network I/F (for example, see patent documents 1 and 2).
A power-saving mode is achieved as follows. That is, a power-saving status is implemented in accordance with the status of the image forming apparatus by stopping the power from the power supply to the engine and the main CPU. The engine is used for forming toner images based on image data, printing the toner images onto sheets, and ejecting the sheets with the printed images to the outside. The main CPU controls the entire apparatus and printing operations. When it is necessary to use the engine and the main CPU, the mode returns to a regular power feeding status, so that the engine and the main CPU can be operated.
Furthermore, the following technique has been proposed (see, for example, patent document 3) to enhance the effects of power conservation in the power-saving mode. Specifically, an ASIC is provided separately from the main CPU for returning from the power-saving status, in which the power supply to the main CPU is stopped, to the regular operation mode, via a network. Thus, the ASIC can operate while the power supply to the main CPU is stopped, so that when there is access via the network, the main CPU can return to the regular operation mode from the power-saving mode.    Patent Document 1: Japanese Laid-Open Patent Application No. 2002-268471    Patent Document 2: Japanese Laid-Open Patent Application No. 2003-89254    Patent Document 3: Japanese Laid-Open Patent Application No. 2005-94679
However, in the above conventional techniques, when both the engine and the main CPU are in a power-saving mode, and both need to return to the regular operation mode, the following operation is performed. First, the main CPU returns to the regular operation mode, and then the main CPU causes the engine to return to the regular operation mode. When the engine receives power and becomes activated, the engine starts communications with the main CPU (referred to as “RAPI communications”), in order to set various modes and perform the printing operation. Thus, it takes a long time until the first sheet can be copied in a copying operation, for example. This degrades the convenience for the user.